Quartz synchronised clockwork

ABSTRACT

In quartz synchronised electrical apparatus for controlling a clock movement driven by electrical impulses to a driving winding, the isochronism of the balance is degraded to render the frequency of oscillation dependent on the amplitude. A quartz oscillator connected to a frequency dividing circuit supplies impulses at a reference frequency, and controls gating means serving to modify the amplitude of the impulse to the driving winding during impulses at the reference frequency, to restore the actual frequency of oscillation of the balance so as to be equal to the reference frequency.

United States Patent [1 1 [111 3,884,034 Dietsch May 20, 1975 [54] QUARTZ SYNCI-IRONISED CLOCKWORK 3,648,453 3/ gizalvva 22/28 A 14 3 ts ct 2 [75] Inventor: Jacques J. G. Dietsch, Paris, France l a y a l 8 R Assigneei f Anonyme des Primary Examiner-Edith Simmons Jackmon Establlssemems Hatot, Pans, Attorney, Agent, or Firm-Donald D. Jeffery France [22] Filed: Oct. 10, 1973 57 ABSTRACT PP ,916 In quartz synchronised electrical apparatus for controlling a clock movement driven by electrical im- [30] Foreign Application Priority Data pulses to a driving winding, the isochronisrn of the bal- O l 1 1972 F 72 35957 ance is degraded to render the frequency of oscillation fame dependent on the amplitude. A quartz oscillator connected to a frequency dividing circuit supplies img 58/28 g; 321 pulses at a reference frequency, and controls gating i 28 318/128. means serving to modify the amplitude of the impulse 1 0 can: 1/1 16 to the driving winding during impulses at the reference frequency, to restore the actual frequency of oscilla- References Cited tion of the balance so as to be equal to the reference frequency.

7 Claims, 3 Drawing Figures +III DVD

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4m QZ hhhhh bi QUARTZ SYNCHRONISED CLOCKWORK The present invention relates to clockwork movements, and to apparatus for controlling them, and more particularly to electronic arrangements for synchronising a clockwork movement in relation to a quartz oscillator.

When sufficiently small quartz oscillators appeared on the market it was suggested that their very stable frequency might be used in a clock movement. Thus clockwork movements relying wholly on the frequency supplied by a quartz oscillator are already sold, for example in the form of watches.

For the transition of electric signals to the mechanical control of a clockwork movement, these devices in general comprise a step-by-step motor which responds directly to the impulses of the quartz oscillator. Apart from the high quality required for such a motor in order to obtain the intended precision, it is to be noted that a parasitic impulse superimposed on the impulses supplied by the quartz oscillator results in a very great error in relation to the required precision.

The present applicant has proposed, in particular in his U.S, Pat. No, 3,168,690 clockwork movements already having a high precision, comprising a classical clockwork movement of which the balance is provided with a magnetic element. A controlling winding and a driving winding are connected in an electric circuit comprising a transistor and a source of supply, so that the driving winding is traversed by current impulses amplified with respect to those induced in the control winding. The two windings co-operate with the magnetic device to maintain oscillations of the latter at a predetermined maintenance frequency. The balance may be a pendulum or a wheel and hairspring and the term is used herein to include any vibrating system having a natural frequency of vibration.

Variants of these arrangements are known in which the passage of current in the driving winding is controlled by closing of an electric contact, responding to the movement of the balance.

An object of the present invention is to provide an improved apparatus combining a quartz oscillator associated with a frequency dividing circuit with a movement of the above type, preferably without loss of the desired precision. According to the present invention apparatus for controlling a clockwork movement incorporating a balance and a driving winding receiving electric maintenance impulses to co-operate with a magnetic element of the balance to maintain oscillation of the balance with a normal amplitude at a predetermined maintenance frequency includes a quartz oscillator associated with a frequency dividing circuit to supply electric reference impulses at a reference frequency differing slightly from the predetermined maintenance frequency, and gating means serving to modify the amplitude of each maintenance impulse if and so long as it overlaps with a reference impulse, and thereby adjust the actual frequency of oscillation of the balance to make it equal to the reference frequency.

The means for providing maintenance impulses may include a maintenance transistor having its output circuit conncted in series with the driving winding to a supply, and a control winding producing impulses in response to the movement of the balance, connected to the input circuit of the transistor.

In a first embodiment the gating means comprises a resistor in series with the driving winding, and a gating transistor with its collector emitter circuit connected across the resistor, with its base circuit connected to the output of the frequency divider.

In a second embodiment the gating means comprises a gating transistor of which the base circuit is connected to the output of the frequency divider and of which the collector emitter circuit comprises the control winding and the driving winding.

The invention may be put into practice in various ways but two specific embodiments will be described by way of example, with reference to the accompanying drawings, in which:

FIGS. 1 and 2 are circuit diagrams respectively of two arrangements for synchronising a clockwork movement with a quartz oscillator, and FIG. 2A is a fragmentary circuit diagram identical to FIG. 2 except that a resistor has been replaced by a diode.

In each embodiment the invention is applied to a clockwork movement provided with a balance having a magnetic element co-operating (as in US, Pat. No. 3,168,690 referred to above) with a control winding BC, a driving winding BM, a maintenance transistor T and a decoupling capacitor C connected in a circuit with a source S.

As in the US. Pat. No. 3,168,690 referred to above the driving winding BM is connected to the source S through the emitter collector path of the maintenance transistor T while the control winding is connected between its emitter and base, and a capacitor C between its base and collector.

In accordance with the invention, in the arrangement of FIG. 1 a resistor R is connected in series with the driving winding BM and is shunted by the emitter collector path of a gating transistor T to enable the amplitude of the maintenance impulses to be varied.

The emitter base circuit of the gating transistor T is connected through a resistor R to the output of an 08- cillatorand frequency dividing circuit DVO controlled by a quartz crystal Q2. (The frequency division may be effected by numerical counting). The frequency divider and oscillator are also powered from the source S. In a manner known in itself the output of the frequency divider provides calibrated reference impulses, and the spacing between these impulses is always the same, defining a reference frequency with very high precision. It will be understood that the width of the impulse can vary substantially, in accordance with the types of frequency divider, to the point at which the signals reach the stage of resembling rather square or rectangular signals. The word impulse will however be 1 used herein for simplicity.

In embodying the invention the balance is chosen or modified to have degraded isochronism, for example by employing a pendulum having a wide angle of swing, or a balance wheel with a modified hairspring To degrade the isochronisme of a balance wheel and hairspring one can, as is known, slightly deform its spiral hair spring or equally one can employ another means of disturbance (magnetic, metallic mass).

In the specific embodiment described the balance has a higher frequency at low amplitude than it has at high amplitude. In this case the natural frequency of the balance is chosen to be lower than the reference fre quency. By natural frequency," one means the predetermined maintenance frequency on which the driving winding may sustain the balance at a normal amplitude, without any synchronising means, according to prior art.

In embodying the invention it is to be noted that the inverse arrangement (the balance having a lower frequency at low amplitude, and its natural frequency being higher than the reference frequency) is also possible.

Thus in operation, assuming that the balance has been started, it oscillates at high amplitude, and hence at a frequency slightly lower than its nominal natural frequency at normal amplitude. On its part the gating transistor T is rendered periodically conducting at the reference frequency by the impulse supplied at the output of the frequency dividing circuit DVO.

Due to the resistor R the maintaining energy applied to the magnetic element of the balance by the driving winding BM is low, and the amplitude of oscillation of the latter rapidly decreases, thereby raising the frequency of oscillation of the balance to tend to recover and pass its nominal value at normal amplitude.

Throughout this period the maintenance impulses supplied to the driving winding and the reference impulses supplied by the output of the circuit D rarely coincide, and they do not change the operation of the system as just described.

On the other hand when the maintenance or actual frequency of oscillation of the balance increases so as to approach the reference frequency, the reference impulses will overlap with the beginnings of the maintenance impulses. The resistor R is therefore bypassed or short-circuited during an initial portion of each maintenance impulse. The result is that each maintenance impulse comprises a first part at high energy and a second part at lower energy. The relative importance of the first part grows when the real frequency of oscillation of the balance further approaches the reference frequency. This then produces an increase of amplitude of the balance, which as noted above tends to reduce the maintenance frequency. It will therefore be understood that the oscillations of the balance adapt themselves to the reference frequency, anyinstantaneous departure tending to be corrected by increase or decrease of the part of the driving impulse during which the transistor T conducts. In mean value the precision of the system is that provided by the quartz oscillator.

It will be noted that a parasitic impulse appearing on the base of the transistor T falls for the most part of the time outside the driving impulse, and is thus inoperative. If it arrives during the maintenance impulse its adverse effect is in any case rapidly corrected.

In the embodiment shown in FIG. 2 the resistor R is connected between the base of the transistor T and the collector of the transistor T of which the emitter is connected to the positive terminal of the source S.

The other connections are identical to those of the arrangement of FIG. 1.

The operation takes place in substantially the same way as for the embodiment of FIG. 1, taking into account however that the conduction of the transistor T during the reference impulses is liable to produce diminution of the amplitude of the maintaining impulse, and not an increase as in the first embodiment. The result is that the reference impulses this time produce diminution of amplitude in a later portion of the maintaining impulses.

In the embodiment shown in FIG. 2A, all elements and circuits are identical to these of FIG. 2, except that resistor R has been replaced by diode d although it will be understood that more than one diode may be employed. In this case it is the duration of the maintenance impulse that is modified.

Moreover it may be noted in either case, the intermittent opposing torque produced by the train of the clockwork movement produces a reduction of amplitude of the balance, but that the frequency is immediately corrected by a change of the maintenance impulse which compensates for the energy absorbed.

' Moreover the systems which have been described can be arranged to continue to function even if the reference impulses disappear; admittedly the accuracy is then rather poor.

It will also be noted that the energy necessary for maintaining the quartz-controlled movement according to the invention is less than that, already low, which is required for the known electrical maintenance of oscillation of the balance described in the U.S. Pat No. 3,168,690 referred to: in FIG. 1 this results from the inclusion of the series resistor R in FIG. 2, it results from reduction of amplitude or ofduration of the maintaining impulses.

The embodiment of FIG. 1 is also directly applicable for the synchronisation of clockwork movements with an electrical contact actuated in time with the movement of the balance.

The arrangements described are compatible with already existing clockwork movements, and, in particular, those in accordance with the U.S. Pat. No.

3,168,690 referred to above, which avoids numerous problems in connection with their public distribution.

According to the types of frequency-dividing circuits utilised the output impulses can have different polarities with respect to the potential V of the supply. Depending on the case the gating transistor T will be of PNP or NPN type, and will be connected to one pole or the other of the source of supply.

What we claim as our invention and desire to secure Letters Patent is:

1. Apparatus for controlling a clockwork movement incorporating a balance and a driving winding receiving electric maintenance impulses to co-operate with a magnetic element of the balance to maintain oscillation of the balance with a normal amplitude at a predetermined maintenance frequency, said apparatus comprising a quartz oscillator operatively associated with a frequency 'div iding circuit having an output supplying electric reference impulses at a reference frequency differing slightly from the predetermined maintenance frequency, and gating means operatively connected to said output to modify the amplitude of each maintenance impulse if and so long as it overlaps with a reference impulse, and thereby adjust the actual frequency of oscillation of the balance to make it equal to the reference frequency.

2. Apparatus as claimed in claim 1 in which the means for providing maintenance impulses include a maintenance transistor having its output circuit connected in series with the driving winding to a supply, and a control winding producing impulses in response to the movement of the balance, connected to the input circuit of the transistor.

3. Apparatus as claimed in claim 2 in which the gating means comprise a resistor in series with the driving 6 collector emitter circuit also includes a resistor.

6. Apparatus as claimed in claim 4 in which the said collector emitter circuit also includes diode means connected in the conducting direction.

7. Apparatus as claimed in claim 2 in which the quartz oscillator, the frequency divider and the means for providing maintenance impulses are all fed from a common source of supply. 

1. Apparatus for controlling a clockwork movement incorporating a balance and a driving winding receiving electric maintenance impulses to co-operate with a magnetic element of the balance to maintain oscillation of the balance with a normal amplitude at a predetermined maintenance frequency, said apparatus comprising a quartz oscillator operatively associated with a frequency dividing circuit having an output supplying electric reference impulses at a reference frequency differing slightly from the predetermined maintenance frequency, and gating means operatively connected to said output to modify the amplitude of each maintenance impulse if and so long as it overlaps with a reference impulse, and thereby adjust the actual frequency of oscillation of the balance to make it equal to the reference frequency.
 2. Apparatus as claimed in claim 1 in which the means for providing maintenance impulses include a maintenance transistor having its output circuit connected in series with the driving winding to a supply, and a control winding producing impulses in response to the movement of the balance, connected to the input circuit of the transistor.
 3. Apparatus as claimed in claim 2 in which the gating means comprise a resistor in series with the driving winding, and a gating transistor with its collector emitter circuit connected across the resistor, and its base circuit connected to the output of the frequency divider.
 4. Apparatus as claimed in claim 2 in which the gating means comprise a gating transistor of which the base circuit is connected to the output of the frequency divider and of which the collector emitter circuit comprises the control winding and the driving winding.
 5. Apparatus as claimed in claim 4 in which the said collector emitter circuit also includes a resistor.
 6. Apparatus as claimed in claim 4 in which the said collector emitter circuit also includes diode means connected in the conducting direction.
 7. Apparatus as claimed in claim 2 in which the quartz oscillator, the frequency divider and the means for providing maintenance impulses are all fed from a common source of supply. 